1. Field of the Invention
The present disclosure relates to power converters, and more particularly to multilevel inverters for converting direct current (DC) voltage into alternating current (AC) voltage.
2. Description of Related Art
Inverters convert DC power into AC power. Multilevel inverters employ multiple voltage levels and solid-state switch devices. A controller cycles the solid-state switch devices between on and off states to generate output AC voltage, generally with a stepped waveform approximating a sinusoidal waveform. The solid-state switch devices are typically grouped into phase legs uniformly consisting of either integrated gate bipolar transistors (IGBTs) or field effect transistors (MOSFETs).
IGBT-based inverters are generally preferred in high-voltage, low switching frequency applications because IGBTs exhibit high switching losses at high switching frequencies. Because they generally operate at low frequencies, IGBT-based inverters typically require additional output filtering to smooth the output stepped AC voltage waveform.
MOSFET-based inverters are generally used in low-voltage applications with high switching frequencies due to their relatively low losses. Because they operate at higher frequencies there is less need for filtering, allowing for the use of smaller filter components. However, due to the highly nonlinear output capacitance associated with MOSFET devices, voltage balancing between MOSFETs in a given phase leg can pose challenges, potentially reducing device reliability.
Such conventional methods and systems for power conversion have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved converters. The present disclosure provides a solution for this need.